Measurement of the adiabatic flame speed and overall activation energy of a methane enriched H2/CO/CO2/N2 low heating value mixture

2020 ◽  
Vol 45 (53) ◽  
pp. 29533-29545
Author(s):  
Roberto Wolf Francisco ◽  
Amir Antônio Martins Oliveira
Keyword(s):  
Activation Energy ◽  
Flame Speed ◽  
Heating Value

scholarly journals Torrefaction of Sewage Sludge: Kinetics and Fuel Properties of Biochars

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 565 ◽  
Author(s):  
Jakub Pulka ◽  
Piotr Manczarski ◽  
Jacek Koziel ◽  
Andrzej Białowiec
Keyword(s):  
Activation Energy ◽  
Sewage Sludge ◽  
Thermal Transformation ◽  
Fuel Properties ◽  
Process Time ◽  
Technological Aspect ◽  
Heating Value ◽  
Valuable Product ◽  
Kinetics Of

We propose a ‘Waste to Carbon’ thermal transformation of sewage sludge (SS) via torrefaction to a valuable product (fuel) with a high content of carbon. One important, technological aspect to develop this concept is the determination of activation energy needed for torrefaction. Thus, this research aimed to evaluate the kinetics of SS torrefaction and determine the effects of process temperature on fuel properties of torrefied products (biochars). Torrefaction was performed using high ash content SS at six (200~300 °C) temperatures and 60 min residence (process) time. Mass loss during torrefaction ranged from 10~20%. The resulting activation energy for SS torrefaction was ~12.007 kJ·mol−1. Initial (unprocessed) SS higher heating value (HHV) was 13.5 MJ·kg−1. However, the increase of torrefaction temperature decreased HHV from 13.4 to 3.8 MJ·kg−1. Elemental analysis showed a significant decrease of the H/C ratio that occurred during torrefaction, while the O/C ratio fluctuated with much smaller differences. Although the activation energy was significantly lower compared with lignocellulosic materials, low-temperature SS torrefaction technology could be explored for further SS stabilization and utilization (e.g., dewatering and hygienization).

Thermochemical properties of energy crop species planted in Slovakia

BioResources ◽  
2020 ◽  
Vol 16 (1) ◽  
pp. 764-778
Author(s):  
Andrea Majlingová ◽  
Martin Lieskovský ◽  
Milan Oravec ◽  
Marek Trenčiansky ◽  
Rastislav Veľas
Keyword(s):  
Activation Energy ◽  
Chemical Properties ◽  
Arundo Donax ◽  
Energy Crops ◽  
Energy Crop ◽  
Small Scale ◽  
Agricultural Activity ◽  
Crop Species ◽  
Heating Value ◽  
Miscanthus Giganteus

In the last decades, a new phenomenon has arisen in connection with temporary or permanent non-use of land for agricultural activity, namely the cultivation of energy crops in these localities, because of growing demand for biomass as a fuel. Farmers are expected to sell energy crops and the fuels they produce, both at home and in the surrounding countries. To choose economically efficient energy crop species to cultivate, the thermochemical parameters of the crop should be used to support decision-making process of farmers. This paper summarizes the results of small-scale laboratory tests of three energy crop species planted in Slovakia – Sida hermaphrodita, Arundo donax, and Miscanthus × giganteus – used for determination of thermal and chemical properties of the energy crop species to evaluate their suitability for energy purposes. The most suitable species for energy purposes was found to be Miscanthus × giganteus with higher heating value of 19.6 MJ/kg, lower heating value of 14.8 MJ/kg (at moisture content of 17%), and ash mass of 2.67% dry mass (d.m.). From a lignin mass and activation energy point of view, the most suitable for energy purposes was Arundo donax, with a lignin mass of 20.5% d.m. and an activation energy of 124.2 kJ/mol.

PULSATING INSTABILITIES OF COMBUSTION WAVES IN A CHAIN-BRANCHING REACTION MODEL

2009 ◽  
Vol 19 (03) ◽  
pp. 873-887 ◽  
Author(s):  
V. V. GUBERNOV ◽  
A. V. KOLOBOV ◽  
A. A. POLEZHAEV ◽  
H. S. SIDHU ◽  
G. N. MERCER
Keyword(s):  
Activation Energy ◽  
Hopf Bifurcation ◽  
Combustion Wave ◽  
Traveling Wave ◽  
Lewis Number ◽  
Flame Speed ◽  
Traveling Wave Solution ◽  
Solution Branch ◽  
Combustion Waves ◽  
Parameter Values

In this paper we investigate the properties and linear stability of traveling premixed combustion waves and the formation of pulsating combustion waves in a model with two-step chain-branching reaction mechanism. These calculations are undertaken in the adiabatic limit, in one spatial dimension and for the case of arbitrary Lewis numbers for fuel and radicals. It is shown that the Lewis number for fuel has a significant effect on the properties and stability of premixed flames, whereas varying the Lewis number for the radicals has only qualitative (but not qualitative) effect on the combustion waves. We demonstrate that when the Lewis number for fuel is less than unity, the flame speed is unique and is a monotonically decreasing function of the dimensionless activation energy. Moreover, in this case, the combustion wave is stable and exhibits extinction for finite values of activation energy as the flame speed decreases to zero. However, for the fuel Lewis number greater than unity, the flame speed is a C-shaped and double valued function. The linear stability of the traveling wave solution was determined using the Evans function method. The slow solution branch is shown to be unstable whereas the fast solution branch is stable or exhibits the onset of pulsating instabilities via a Hopf bifurcation. The critical parameter values for the Hopf bifurcation and extinction are found and the detailed map for the onset of pulsating instabilities is determined. We show that a Bogdanov—Takens bifurcation is responsible for both the change in the behavior of the traveling wave solution near the point of extinction from unique to double valued type as well as for the onset of pulsating instabilities. We investigate the properties of the Hopf bifurcation and the emerging pulsating combustion wave solutions. It is demonstrated that the Hopf bifurcation observed in our present study is of supercritical type. We show that the pulsating combustion wave propagates with the average speed smaller than the speed of the traveling combustion wave and at certain parameter values the pulsating wave exhibits a period doubling bifurcation.

scholarly journals Analisis Energi Aktivasi Pada Variasi Kecepatan Udara Dan Laju Reaksi Pembakaran Briket Limbah Kelapa Tua, Kelapa Muda Dan Kakao

2019 ◽  
Vol 20 (2) ◽  
pp. 48-52
Author(s):  
Wahidin Nuriana ◽  
Agus Suryanto ◽  
Mustafa Kamal
Keyword(s):  
Activation Energy ◽  
Raw Materials ◽  
Combustion Process ◽  
Calorific Value ◽  
Biomass Waste ◽  
Heating Value ◽  
Thermal Gravimetry ◽  
Rate Of Combustion ◽  
Air Heating ◽  
Air Speed

The purpose of this study was to obtain activation energy with the rate of combustion air, reduced mass weight and reaction rate of combustion of charcoal briquettes from biomass waste of old coconut, young coconut, cacao waste with carbonization at a temperature of 400oC, for 30, 60, 90 and 120 minutes. The study was conducted in a laboratory, with 3 (three) repetitions. The study was carried out by sorting raw materials, chopping, drying, carbonizing, grinding, sifting, adding tapioca glue to print, and pressing at 115 kg / cm2. The results of the briquette were analyzed for heat, the highest calorific value of old coconut waste, young coconut, cocoa waste was analyzed for activation energy during the combustion process using DSC by varying the air heating rate of 20, 30, 40 ml / minute. The highest yield of old coconut briquette heating value is 6,927 cal/g with 90 minutes carbonization time. The lowest activation energy is 133.20 joules / gram on old coconut briquettes with an air speed of 40 ml / minute. In the rate of combustion reaction by thermogravimetry with Thermal Gravimetry Analyzer (TGA), the greatest reduction in mass weight on old coconut waste briquettes compared to young coconut and cocoa waste briquettes was 55.34% from 590.5 oC to 599.2 oC.

scholarly journals Preparation of biochar via dry torrefaction of wood meal in a batch reactor under pressure and its co-combustion behavior with anthracite coal

BioResources ◽  
2020 ◽  
Vol 16 (1) ◽  
pp. 997-1008
Author(s):  
Wei Yang ◽  
Fan Yang ◽  
Xu Zhang ◽  
Pengfei Zhu ◽  
Huanghu Peng ◽  
...  
Keyword(s):  
Activation Energy ◽  
Lower Energy ◽  
Batch Reactor ◽  
Synergetic Effect ◽  
Obvious Effect ◽  
Heating Value ◽  
Optimal Ratio ◽  
Wood Meal ◽  
Combustion Behavior ◽  
Anthracite Coal

Biochar was prepared by dry torrefaction of wood meal in a batch reactor under pressurized conditions. The biochar prepared at 340 °C (WMB-340) showed a higher heating value (HHV) of 30.5 MJ/kg, and it was employed to co-combust with anthracite coal (AC) with the HHV of 28 MJ/kg. The WMB-340 underwent two combustion stages, while the AC only showed one combustion stage. The combustion of AC was promoted by WMB-340 at temperatures higher than 490 °C, indicating the existence of a synergetic effect during co-combustion. Blending AC with 10% WMB-340 had no obvious effect on the combustion stage of AC. However, three combustion stages existed when blending more than 10% WMB-340 with AC. The activation energy of AC blended with 10% WMB-340 was 84.5 kJ mol-1, much lower than that of AC (179.3 kJ mol-1), indicating a lower energy for initialization of the blend. Therefore, AC blended with 10% WMB-340 was the optimal ratio for co-combustion in this study.

scholarly journals Co-Pyrolysis of Beet Pulp and Defecation Lime in TG-MS System

Energies ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2304
Author(s):  
Radosław Slezak ◽  
Liliana Krzystek ◽  
Piotr Dziugan ◽  
Stanisław Ledakowicz
Keyword(s):  
Activation Energy ◽  
Calcium Carbonate ◽  
Sugar Beet ◽  
Production Yield ◽  
Pyrolysis Process ◽  
Heating Value ◽  
Calcination Process ◽  
Raw Sugar ◽  
Beet Pulp ◽  
Isoconversion Method

The process of pyrolysis of beet pulp, a by-product after the extraction of raw sugar from sugar beet, with the addition of defecation lime was studied in a thermobalance coupled with a mass spectrometer. The beet pulp pyrolysis process took place completely at 600 °C, and the resulting char, tar and gas were characterized by higher heating values of 23.9, 21.6 and 7.77 MJ/kg, respectively. The addition of the defecation lime to beet pulp caused both an increase in the char production yield and a decrease in the tar production yield. At the same time, the higher heating value of char and tar decreased along with the increase of defecation lime added to the sample. The deconvolution of derivative thermogravimetric (DTG) curves allowed us to identify the basic components of beet pulp, for which the activation energy by isoconversion method was calculated. The 20 wt.% addition of defecation lime caused an increase of the activation energy by about 18%. Further increase in the defecation lime content resulted in a reduction of activation energy. At the temperature above 600 °C, calcination of calcium carbonate contained in defecation lime occurred. The CO2 produced during calcination process did not cause auto-gasification of char.

High Temperature n- and p-type Doped Microcrystalline Silicon Layers Grown by VHF PECVD Layer-by-Layer Deposition

2003 ◽  
Vol 762 ◽  
Author(s):  
A. Gordijn ◽  
J.K. Rath ◽  
R.E.I. Schropp
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
High Temperatures ◽  
Continuous Wave ◽  
Hydrogen Plasma ◽  
Silicon Layer ◽  
Dark Conductivity ◽  
High Deposition Rate ◽  
Layer By Layer ◽  
Microcrystalline Silicon

AbstractDue to the high temperatures used for high deposition rate microcrystalline (μc-Si:H) and polycrystalline silicon, there is a need for compact and temperature-stable doped layers. In this study we report on films grown by the layer-by-layer method (LbL) using VHF PECVD. Growth of an amorphous silicon layer is alternated by a hydrogen plasma treatment. In LbL, the surface reactions are separated time-wise from the nucleation in the bulk. We observed that it is possible to incorporate dopant atoms in the layer, without disturbing the nucleation. Even at high substrate temperatures (up to 400°C) doped layers can be made microcrystalline. At these temperatures, in the continuous wave case, crystallinity is hindered, which is generally attributed to the out-diffusion of hydrogen from the surface and the presence of impurities (dopants).We observe that the parameter window for the treatment time for p-layers is smaller compared to n-layers. Moreover we observe that for high temperatures, the nucleation of p-layers is more adversely affected than for n-layers. Thin, doped layers have been structurally, optically and electrically characterized. The best n-layer made at 400°C, with a thickness of only 31 nm, had an activation energy of 0.056 eV and a dark conductivity of 2.7 S/cm, while the best p-layer made at 350°C, with a thickness of 29 nm, had an activation energy of 0.11 V and a dark conductivity of 0.1 S/cm. The suitability of these high temperature n-layers has been demonstrated in an n-i-p microcrystalline silicon solar cell with an unoptimized μc-Si:H i-layer deposited at 250°C and without buffer. The Voc of the cell is 0.48 V and the fill factor is 70 %.

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